Abstract: The dissimilar materials of Ni-base cast superalloy K447A and Ni-base wrought superalloy GH4169 were welded by Inertia Friction Welding (IFW). The microstructure and high temperature mechanical properties of the joints were studied after heat treatment. The results show that good flash can be formed after IFW and no clear defects were found at the root of the flash. Fine recrystallization zone was formed in the weld zone (WZ) and fine γ'' phase and γ' phase were precipitated in the WZ after heat processing. The recrystallization zone width of the K447A side is between 3μm and 10μm. The high temperature tensile strength and torsional strength of GH4169 + K447A IFW joints were equal to K447A base metal. The high cycle fatigue strength of the joint is 355 MPa at the temperature of 400 °C. Under the condition of 400 °C and 720 MPa, the low cycle fatigue life of all the joint samples exceeded 30 000 times.